SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: bbfsouthwind on June 24, 2009, 07:42:47 PM
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I just installed new autometer marine gauges in my boat. Everything works well except for the tach. I have checked over and over the settings on the tach, they are correct for 8cyl operation. I have an older mallory ignition box and a single point distrubutor. New wiring on the engine with all soldered connections. Problem is that the tach seems to read correctly until you go wide open throttle. Then it goes past 6k rpms. I know the engine isnt turning that fast. I have the tach wire from the box going to my terminal block then up to the tach, ground is from the terminal block up to the tach. What could be causing this problem? Do i need some kind of filter on the ground wire to prevent this or what?
Thanks
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Check the switch on the back and make sure its on the v-8 setting. I don't remeber which setting its supposed to be on but I just turned mine while on the water running until it read correctly. the instructions from the tach should tell you. if its not that someone else will need to chime in...
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from the autometer website.
My Tach Registers/Shows the Wrong RPM?
The causes of this type of problem can vary. We recommend that you check the following before contacting our Tech Department:
1.) Our tachometers come pre-set from the factory as 8 cylinder. Has the tachometer been properly adjusted/calibrated for your application?
2.) An insufficient power or ground will cause a tachometer to actually read too high. If you are experiencing this problem, perform the following:
Using a voltmeter (not a test light), measure across the Red wire and Black wire coming from the tachometer while the engine is running. DO NOT USE AN ALTERNATE GROUND! By doing this, you will be looking at what the tachometer sees for power and ground, combined. If you measure below 12.0 volts, identify which connection is the problem, and correct it.
3.) If you find that your tachometer is off by a very small amount (such as 2 to 400 rpm), consider what you are comparing it to. Many factory tachometers are slow to respond due to heavy dampening used for smoothing pointer operation.
4.) If you are using something other that a 4, 6, or 8 cylinder application then make the tachometer you chose is correct for your application.
If after checking these items, you feel that your Auto Meter tachometer is still off calibration, please visit the Contact Us or Ask A Question pages to inquire about how you may send it in to us for service.
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I have checked over and over the settings on the tach, they are correct for 8cyl operation.
Check the switch on the back and make sure its on the v-8 setting. I don't remeber which setting its supposed to be on but I just turned mine while on the water running until it read correctly. the instructions from the tach should tell you. if its not that someone else will need to chime in...
HMMM. :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead:
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The tach has 3 switches on the inside, i have triple checked the switch positions and they are in the correct position for a v8. I will check again tomorrow and maybe toggle them back and forth and see if that will help but i am thinking maybe i need a inline filter on the signal wire? Or maybe a noise filter on the ground wire?
Thanks
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Based on the #2 Trouble shoot comment they make on their site, check ground wire situation. All of my gage problems have ultimately been grounding issues.
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will check the tach with a voltmeter and run an auxillary ground wire directly to the battery when i take it out tomorrow. I will keep you guys updated, thanks alot for the help!!
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HMMM. :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead:
oops missed that.
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will check the tach with a voltmeter and run an auxillary ground wire directly to the battery when i take it out tomorrow. I will keep you guys updated, thanks alot for the help!!
A bad condenser/loose connection will do that also, did the old tach work?
GT
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Old tach was a pos, it was stuck in one position with a spider inside of it. So i'm not really sure on that.
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tach has 12.3 volts to it with the key on, the ground goes back to the block, i have a terminal block thing that distributes the ground to the gauges, horn and radio under the dash. Could this be causing my problem? Does the tach need its own seperate ground wire with no interference?
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tach has 12.3 volts to it with the key on, the ground goes back to the block, i have a terminal block thing that distributes the ground to the gauges, horn and radio under the dash. Could this be causing my problem? Does the tach need its own seperate ground wire with no interference?
No.
;D
GT
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Are you sure you have a good uncorroded ground wire? Seen wires look good and the middle looked like crap. Doesnt hurt to run a new one and doesnt take that long.
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Ran a new ground wire today just for the tach straight from the ground on my terminal block in the rear of the boat. Going to test it out next week. Got a few other things to work out, hopefully all goes well O0
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good luck!